1. Field of the Invention
The present invention generally relates to an information record medium, and more particularly to an information record medium on which information can be optically recorded and reproduced in accompaniment with a tracking servo control of a so-called push-pull method.
2. Description of the Related Art
There is a DVD as an information record medium, whose record capacity is improved to be as high as several times of that of a conventional CD (Compact Disc), and on which video information and audio information in an information amount of one full move or the like can be recorded.
Other than the DVD dedicated for reproduction such as a DVD-ROM (DVD-Read Only), there is a so-called DVD-RW (DVD Re-recordable) as a DVD standard, on which the information can be reproduced and recorded at a plurality of times, and on which the information can be reproduced by an information reproducing apparatus for reproducing the DVD dedicated for reproduction.
Here, on an information record medium based on the DVD-RW standard, there is formed a groove track, which has a width of about 0.3 xcexcm and a depth of about 20 nm (nanometer) and which is wobbled at a constant frequency, as an information track on which the optical information recording and reproduction is performed. At this time, the reason why the groove track is wobbled is to generate a record standard clock signal having an accurate frequency synchronous with the rotation of the DVD-RW, by detecting the frequency of the wobbling at the time of information recording.
On the other hand, the DVD-RW basically has a record capacity substantially same as that of the DVD dedicated for reproduction. Thus, the video information etc., recorded on the DVD dedicated for reproduction may be illegally copied onto the DVD-RW. At this time, the video information or the like recorded on the DVD dedicated for reproduction is generally protected by a copy right, so that the copy right holder drastically suffers losses if the above mentioned illegal copy is often performed.
Therefore, there is a countermeasure against such an illegal copy according to the DVD-RW standard that the area on the DVD-RW, which corresponds to the area where control information for controlling the reproduction is recorded on the DVD dedicated for reproduction, is set as an area where recording is impossible on the DVD-RW, to thereby prevent the illegal copy.
In addition to this, according to the DVD-RW standard, it is permitted to prepare an area dedicated for reproduction on the above mentioned area where recording is impossible, and to record the predetermined reproduction control information etc., in advance in this area. Further, according to the DVD-RW standard, the phase pit, which is used in the DVD dedicated for reproduction, is also used to record this predetermined reproduction control information etc., in the area dedicated for reproduction of the DVD-RW.
On the other hand, according to the DVD-RW standard, at the time of optically recording and/or reproducing the information by use of the light beam such as a laser light with respect to the DVD-RW, the tracking servo control is performed by means of the so-called push-pull method.
However, if it is attempted to obtain the tracking error signal by the push-pull method at the time of reproducing the reproduction control information, which is recorded in the area dedicated for reproduction by forming the phase pit, it may be difficult to obtain the tracking error signal and a detection signal corresponding to the reproduction control information at an adequate signal quality, because of an influence of an interference with a pre-pit formed in the area dedicated for reproduction in advance (i.e., a pre-pit, which is formed within a land track formed adjacent to the groove track and is to record address information (i.e., address information indicating a record position on the DVD-RW) which is used when recording the information onto the groove track other than the area dedicated for reproduction), which is a problem.
It is therefore an object of the present invention to provide an information record medium, on which the detection signal corresponding to the reproduction control information and the tracking error signal by means of the push-pull method can be obtained at adequate signal qualities, in case that the reproduction control information is reproduced from the area dedicated for reproduction on the DVD-RW.
The above object of the present invention can be achieved by an information record medium, on which information is optically recorded and reproduced while a servo control is performed with respect to the information record medium by a push-pull method. The information record medium is provided with: a record/reproduction area having a groove track, which is wobbled and continuously formed and on which the information is recorded and reproduced by a phase changing method by use of a light beam having a wavelength of not less than 630 nm (nanometer) and not more than 680 nm; and a reproduction-dedicated area where a plurality of phase pits are wobbled and formed in advance, each having a depth of not less than 60 nm and not more than 90 nm and where only an information reproduction is possible by the light beam.
According to the information record medium of the present invention, since the phase pit formed in the reproduction-dedicated area has the depth of not less than 60 nm and not more than 90 nm, it is possible to obtain both of (i) a detection signal corresponding to the information to be reproduced by an enough output level by the light beam for recording and reproducing having the wavelength in the above mentioned range and (ii) an error signal for a servo control of the push-pull method, in the reproduction-dedicated area.
In this manner, it is possible to prevent an illegal copy with respect to the information record medium and an illegal reproduction of the illegally copied information, by preparing the reproduction-dedicated area where only the reproduction is possible, and it is also possible to record the necessary information in advance such as the copy control information or the like by using the phase pit within the reproduction-dedicated area and then appropriately reproduce the necessary information.
In one aspect of the information record medium of the present invention, the depth of the phase pit is not less than 70 nm and not more than 80 nm.
According to this aspect, since the depth of the phase pit formed in the reproduction-dedicated area is not less than 70 nm and not more than 80 nm, it is possible to obtain the detection signal and the error signal at the higher output levels.
In another aspect of the information record medium of the present invention, a pre-pit indicating address information, which corresponds to a record position on the information record medium, of the information, is formed within at least the record/reproduction area except the reproduction-dedicated area.
According to this aspect, it is possible to prevent the operation of obtaining the detection signal and the error signal from the reproduction-dedicated area from being disturbed by the pre-pit.
In another aspect of the information record medium of the present invention, unreadable area, which has a plurality of phase pits wobbled and formed in advance and where it is not possible to record or reproduce the information by the light beam, is further formed between the reproduction-dedicated area and the record/reproduction area on the information record medium.
According to this aspect, since the unreadable area is formed between the reproduction-dedicated area and the record/reproduction area, it is possible to avoid an illegal copy and an illegal reproduction with respect to the information record medium, by the existences of the unreadable area and the reproduction-dedicated area.
In this aspect, a pre-pit may be formed within the unreadable area, and the address information indicated by the pre-pit within the unreadable area, may be set on the basis of the address information corresponding to a head of the record/reproduction area within the information record medium.
By constructing in this manner, it is possible to record the information with respect to the record/reproduction area while grasping the record position accurately without being influenced by the existence of the reproduction-dedicated area.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings briefly described below.